JP2008037139A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing pattern noise and suppressing a wandering phenomenon while keeping hydro performance and steering stability good. <P>SOLUTION: At least three main grooves 11 making straight lines are provided on a tread surface 1, and two sub grooves 12 which are linear and thinner/narrower than the all main grooves 11 are provided on both sides of the center main groove 11. A land part 21 is divided in a center area A1 regulated inside of those sub grooves 12, and a land part 22 is divided in an outside area A2 regulated outside of the sub groove 12. A plurality of lug grooves 14 is provided on the land part 22 to divide the land part 22 into a plurality of blocks. At least one of side wall surfaces of each main groove 11 is chamfered, and a cross-section outline shape of a chamfering portion 11a is made to be an arc contacting with the tread surface 1. A ratio of groove width GW2 at a center position in a depth direction to groove width GW1 on the tread surface 1 of each main groove is made to be 30 to 55%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having at least three main grooves extending in the tire circumferential direction on a tread surface, and more particularly, reducing pattern noise and wandering while maintaining good hydro performance and steering stability. The present invention relates to a pneumatic tire that can suppress the phenomenon.

  In pneumatic tires, at least three main grooves extending in the tire circumferential direction are provided on the tread surface, and both hydro performance and steering stability are achieved while exhibiting excellent hydro performance based on the drainage capacity of these main grooves. (For example, refer to Patent Document 1).

However, in the pneumatic tire, not only the hydro performance and the handling stability are improved, but also the pattern noise caused by the air column resonance of the main groove is reduced (for example, see Patent Document 2), and further, the main groove side It is required to suppress a wandering phenomenon caused by a wall surface being caught by a rain groove formed on a road surface (see, for example, Patent Document 3), and it is difficult to satisfy these simultaneously in one tread pattern. is the current situation.
JP 2001-219718 A JP 2000-127713 A JP-A-7-195910

  An object of the present invention is to provide a pneumatic tire that can reduce pattern noise and suppress a wandering phenomenon while maintaining good hydro performance and steering stability.

  In order to achieve the above object, the pneumatic tire of the present invention is provided with at least three main grooves extending linearly in the tire circumferential direction on the tread surface, and the tire circumference on both sides of the main groove located at the center of the tread surface. Two sub-grooves that extend in a straight line in the direction and are narrower than all the main grooves are provided, and a first region sandwiched between the sub-groove and the central main groove in a central region defined inside the sub-grooves. A land portion is defined, a second land portion is defined in an outer region defined on the outside of the sub-groove, and is sandwiched between the sub-groove and a shoulder-side main groove, and the sub-groove is formed in the second land portion. And a plurality of lug grooves opened in the main groove on the shoulder side to divide the second land portion into a plurality of blocks, and chamfering at least one of the side wall surfaces of each main groove, the chamfered portion The cross-sectional profile of the arc is a circular arc in contact with the tread surface, and the grooves in the tread surface of each main groove The ratio of the groove width GW2 of the depth direction central position relative to GW1 is characterized in that it has 30% to 55%.

  In the present invention, by forming a smoothly curved chamfered portion on at least one of the side wall surfaces of each main groove, the lateral force received when the side wall surface of the main groove is caught by the rain groove on the road surface is reduced, and the wandering phenomenon Suppress. In forming the chamfered portion in each main groove, in addition to the cross-sectional contour shape of the chamfered portion being an arc in contact with the tread surface, the groove width GW1 on the tread surface of each main groove and the central position in the depth direction By defining the ratio of the groove width GW2 within the above range, the cross-sectional area of each main groove can be reduced and the air column resonance can be reduced. On the other hand, since the cross-sectional contour of the chamfered portion is an arc in contact with the tread surface, the groove width GW1 at the tread surface of each main groove is increased to increase the contact pressure of the land portion. To contribute. In addition, the provision of sub-grooves that are narrower and narrower than all the main grooves on both sides of the main groove located in the center of the tread surface minimizes the decrease in shear rigidity of the first land portion located in the central area, and controls Contributes to improved stability. This makes it possible to reduce pattern noise and suppress wandering while maintaining good hydro performance and steering stability.

  The sub-groove contributes to improvement of wear resistance performance by reducing surface deformation resistance of the tread surface, and also contributes to an increase in edge effect when turning on a wet road surface. In addition, dividing the second land portion located in the outer region into a plurality of blocks contributes to reduction of sliding sound and impact sound at the time of ground contact.

  In the present invention, the total sum of the groove widths GW1 on the tread surfaces of all the main grooves is preferably 20% to 35% of the contact width TW of the tread surface. Moreover, it is preferable that the curvature radius R of the chamfered portion of each main groove is 10% to 35% of the groove width GW1 on the tread surface of each main groove. This makes it possible to achieve both a reduction in air column resonance noise and hydro performance at a high level.

  The groove depth GD2 of the sub groove is preferably 30% to 60% of the largest groove depth GD1 of all the main grooves. As a result, it is possible to improve steering stability while achieving improvement in wear resistance performance by reducing deformation resistance of the tread surface and improvement in edge effect when turning on a wet road surface. Also, it is preferable to provide a plurality of shallow grooves opening in the first land portion in the sub-groove and the central main groove, and make the depth of these shallow grooves equal to or less than the groove depth of the sub-groove. Thereby, wear resistance performance can be improved and sliding sound at the time of grounding can be reduced, maintaining steering stability.

  The groove depth of the lug groove formed in the second land portion is larger on the shoulder side than the center side of the tread surface, and the largest groove depth GD1 of all the main grooves and the groove depth GD2 of the sub-grooves. It is preferable to set in the range between. As a result, it is possible to achieve both steering stability and hydro performance, and it is possible to reduce the slip amount of the ground contact portion and improve the noise reduction effect and wear resistance performance. Further, the second land block is provided with a sipe that opens at least in the main groove on the shoulder side, and the depth of the sipe is constant or larger on the shoulder side than the center side of the tread surface, and the second It is good to make it smaller than the groove depth of the deepest part of the lug groove formed in the land part. Thereby, the slip amount of the grounding portion can be reduced, and the noise reduction effect and wear resistance performance can be improved.

  A third land portion located outside the main groove on the shoulder side is defined in the outer region defined on the outer side of the sub-groove, and the tread surface is opened to the main land on the shoulder side in the third land portion. It is preferable to provide a plurality of lug grooves extending to a section between the pattern region end and the grounding region end. Thereby, while improving hydro performance, the slip amount of a grounding part can be reduced and the noise reduction effect and abrasion resistance performance can be improved. Further, the third land portion is provided with a plurality of sipes extending to a section between the pattern region end of the tread surface and the grounding region end while opening in the main groove on the shoulder side, and the groove at the deepest portion of the sipes It is preferable to make the depth smaller than the depth of the deepest part of the lug groove formed in the third land portion. Thereby, the slip amount of the grounding portion can be reduced, and the noise reduction effect and wear resistance performance can be improved.

The angle θ1 formed by the main groove at the opening end to the main groove on the shoulder side by the lug groove formed in the second land portion is preferably set in a range of 30 ° to 70 °. On the other hand, the angle θ2 formed by the lug groove formed in the third land portion and the main groove at the opening end to the main groove on the shoulder side is preferably set in the range of 50 ° to 85 °. Thereby, the impact sound at the time of earthing | grounding can be relieved, without producing uneven wear in a block edge part. At that time, the angles θ1 and θ2 are changed to the tire circumferential direction with two or more values, respectively, and the relationship θ1 _max <θ2 _min is established between the maximum value θ1 _max of the angle θ1 and the minimum value θ2 _min of the angle θ2. It is good to do so. Thereby, the frequency of the impact sound at the time of grounding can be disperse | distributed and a noise level can be reduced.

  The sipe formed in the third land portion is set in the range of 30 ° to 90 ° with the angle θ3 formed by the sipe formed in the second land portion with the main groove at the opening end to the main groove on the shoulder side. Is preferably set in the range of 50 ° to 90 ° with the opening end to the main groove on the shoulder side. In this way, by making the angles θ3 and θ4 formed by the sipe with respect to the main groove in the same direction as the angles θ1 and θ2 of the lug grooves, the cornering force caused by the tread pattern in the direction of canceling the vehicle flow due to the cant on the road surface is obtained. It is possible to further improve the handling stability.

  In the present invention, the static dimensions such as the groove width are measured in a state where the tire is mounted on a standard rim defined by a standard effective in the region where the tire is used and filled with an air pressure of 200 kPa. In particular, the groove width on the tread surface of each main groove is 5% to 15% of the ground contact width.

  The contact width of the tread surface is determined when the tread surface of the tire in the above-mentioned internal pressure filling state is grounded to a flat surface and a load of 80% of the maximum load capacity defined by an effective standard in the region where the tire is used It shall be measured from the ground contact shape.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, FIG. 2 shows an outline of the pneumatic tire of FIG. 1 in a meridian cross section, and FIG. 3 shows a main groove and a pneumatic tire in the pneumatic tire of FIG. The outline in the meridian section of the minor groove is shown.

  As shown in FIGS. 1 and 2, three main grooves 11 extending linearly in the tire circumferential direction are formed in the tread surface 1, and tire tires are provided on both sides of the main groove 11 located in the center of the tread surface 1. Two sub-grooves 12 extending in a straight line in the direction and narrower than all the main grooves 11 are formed. A central region A1 is defined on the inner side of the auxiliary groove 12 in the tire width direction, and an outer region A2 is defined on the outer side of the auxiliary groove 12 in the tire width direction. A land portion 21 (first land portion) sandwiched between the sub-groove 12 and the central main groove 11 is defined in the central region A1, and the sub-groove 12 and the shoulder-side main groove 11 are defined in the outer region A2. A land portion 22 (second land portion) to be sandwiched and a land portion 23 (third land portion) located outside the main groove 11 on the shoulder side are partitioned.

  Both side wall surfaces of each main groove 11 are chamfered. This chamfering may be performed only on the side wall surface on one side of the main groove 11. As shown in FIG. 3, the cross-sectional contour shape of the chamfered portion 11 a of the main groove 11 is an arc in contact with the tread surface 1, and the groove at the center position in the depth direction with respect to the groove width GW1 on the tread surface 1 of each main groove 11. The ratio of the width GW2 is set in the range of 30% to 55%.

  By forming the smoothly curved chamfered portion 11a on the side wall surface of the main groove 11 in this way, the lateral force received when the side wall surface of the main groove 11 is caught by the rain groove on the road surface is reduced, thereby suppressing the wandering phenomenon. can do. Further, the cross-sectional contour shape of the chamfered portion 11a is an arc in contact with the tread surface 1, and the ratio of the groove width GW1 on the tread surface 1 of each main groove 11 to the groove width GW2 at the center in the depth direction is defined within the above range. Thereby, the cross-sectional area of each main groove 11 can be made smaller than before, and air column resonance can be reduced. On the other hand, the fact that the cross-sectional contour shape of the chamfered portion 11a is an arc in contact with the tread surface 1 is to increase the contact pressure of the land portions 21 to 23 by increasing the groove width GW1 at the tread surface 1 of each main groove 11. Contributes to improved hydro performance. Here, if the groove width GW2 is less than 30% of the groove width GW1, the cross-sectional area of the main groove 11 decreases, so that the hydro performance deteriorates. Conversely, if the groove width GW2 exceeds 55% of the groove width GW1, air column resonance noise is reduced. The effect is reduced.

  Providing the sub-grooves 12 narrower and narrower than all the main grooves 11 on both sides of the main groove 11 located in the center of the tread surface 1 minimizes a decrease in the shear rigidity of the land portion 21 located in the central area A1, Contributes to improved handling stability. Further, the sub-groove 12 contributes to an improvement in wear resistance by reducing the surface deformation resistance of the tread surface 1 and also contributes to an increase in edge effect when turning on a wet road surface. This makes it possible to reduce pattern noise and suppress wandering while maintaining good hydro performance and steering stability.

  In the pneumatic tire, the total sum of the groove widths GW1 on the tread surface 1 of all the main grooves 11 is set in a range of 20% to 35% of the contact width TW of the tread surface 1. When the above chamfering is adopted, the total groove width GW1 is preferably 20% or more of the ground contact width TW in order to make the hydro performance equal to or higher than that of the conventional one. In order to reduce resonance noise, the total sum of the groove widths GW1 is preferably 35% or less of the ground contact width TW.

  The radius of curvature R of the chamfered portion 11a of each main groove 11 is set in the range of 10% to 35% of the groove width GW1 on the tread surface 1 of each main groove 11. The effect of reducing the air column resonance noise becomes remarkable by setting the curvature radius R of the chamfered portion 11a to 10% or more of the groove width GW1, but in order to avoid a decrease in hydro performance, the curvature radius R is set to 35 of the groove width GW1. % Or less is preferable.

  The groove depth GD2 of the sub-groove 12 is set in a range of 30% to 60% of the largest groove depth GD1 of all the main grooves 11. The groove depth of the main groove 11 may be constant, or may be changed according to the position in the tire width direction, and the largest value among them is defined as the groove depth GD1. The improvement of the wear resistance performance by reducing the deformation resistance of the tread surface 11 and the improvement of the edge effect when turning on a wet road surface appear when the groove depth GD2 is set to 30% or more of the groove depth GD1, but the land portion 21 In order to increase the shear rigidity in the tire width direction and to ensure steering stability, it is preferable to suppress the groove depth GD2 to 60% or less of the groove depth GD1.

  In the land portion 21, a plurality of shallow grooves 13 that are open to the sub-groove 12 and the central main groove 11 are formed at intervals in the tire circumferential direction. The depth of the shallow groove 13 is set equal to or smaller than the depth of the sub-groove 12. Thereby, wear resistance performance can be improved and sliding sound at the time of grounding can be reduced, maintaining steering stability.

  In the land portion 22, a plurality of lug grooves 14 that open to the sub-groove 12 and the main groove 11 on the shoulder side are formed at intervals in the tire circumferential direction. Thereby, the land portion 22 is divided into a plurality of blocks. The groove depth of the lug groove 14 formed in the land portion 22 is larger on the shoulder side than the center side of the tread surface 1, and the largest groove depth GD1 of all the main grooves 11 and the groove depth of the sub-grooves 12. It is set in the range between GD2. When the groove depth of the lug groove 14 is changed in this manner, the shear rigidity in the tire width direction of the tread center side portion of the land portion 22 is increased to ensure cornering power at the time of low load and improve steering stability. be able to. In addition, since the lug groove 14 remains in the shoulder side portion of the land portion 22 even when wear proceeds, the noise reduction effect, wear resistance performance, and hydro performance can be maintained over a long period of time.

  Further, a sipe 15 that opens at least in the main groove on the shoulder side is formed in the block of the land portion 22. The depth of the sipe 15 is fixed or set larger on the shoulder side than the center side of the tread surface 1 and smaller than the depth of the deepest portion of the lug groove 14 formed in the land portion 22. Thereby, the noise reduction effect and the wear resistance performance can be improved.

  In the land portion 23, a plurality of lug grooves 16 are formed at intervals in the tire circumferential direction while opening to the main groove 11 on the shoulder side and extending to a section α between the pattern region end of the tread surface 1 and the ground contact region end. Has been. Here, the end of the pattern area means an outer end of the pattern area where the groove of the tread surface 1 exists, and the pattern area is an area indicated by the width PW. On the other hand, the end of the grounding area means the outer end of the grounding area of the tread surface 1, and the grounding area is an area indicated by the grounding width TW. Thereby, while improving hydro performance, the slip amount of a grounding part can be reduced and the noise reduction effect and abrasion resistance performance can be improved.

  The land portion 23 is formed with a plurality of sipes 17 that open to the main groove 11 on the shoulder side and extend to a section α between the pattern region end and the ground contact region end of the tread surface 1. The depth of the deepest part of the sipe 17 is set to be smaller than the depth of the deepest part of the lug groove 16 formed in the land portion 23. Thereby, the slip amount of the grounding portion can be reduced, and the noise reduction effect and wear resistance performance can be improved.

  As shown in FIG. 1, the angle θ <b> 1 that the lug groove 14 formed in the land portion 22 forms with the main groove 11 at the opening end to the main groove 11 on the shoulder side is set in a range of 30 ° to 70 °. . Thereby, the grounding front end line and the block end line in the land portion 22 intersect with a certain angle, so that the impact sound at the time of grounding can be reduced. In order to obtain the above effect in the block on the tread center side where the contact pressure is high, the angle θ1 needs to be 70 ° or less. However, if the angle θ1 is made excessively small, the block end becomes sharp and uneven wear (capping) occurs. Therefore, in order to avoid this, the angle θ1 is preferably set to 30 ° or more. A preferable range of the angle θ1 is 40 ° to 59 °.

  On the other hand, the angle θ2 that the lug groove 16 formed in the land portion 23 forms with the main groove 11 at the opening end to the main groove 11 on the shoulder side is set in a range of 50 ° to 85 °. As a result, the grounding front end line and the block end line in the land portion 23 intersect each other with a certain angle, so that the impact sound at the time of grounding can be mitigated. However, in order to obtain the above effect in the shoulder side block with a low ground pressure, the angle θ2 may be set to 85 ° or less. On the other hand, the block on the shoulder side has a relatively large slip amount and is liable to cause uneven wear (cupping). Therefore, in order to avoid this, the angle θ2 is preferably set to 50 ° or more. A preferable range of the angle θ2 is 62 ° to 78 °.

When the angles θ1 and θ2 are changed to two or more in the tire circumferential direction, and the relationship θ1 _max <θ2 _min is established between the maximum value θ1 _max of the angle θ1 and the minimum value θ2 _min of the angle θ2. good. Since the frequency of the impact sound at the time of contact is due to the shape of the lug groove, the above conditions are defined in order to reduce the noise level by dispersing the frequency of the generated impact sound. For example, when a pitch variation in which the pitch in the tire circumferential direction of the block element on the tread surface 1 is changed, the angles θ1 and θ2 may be changed together with the pitch variation. For example, 3 to 5 values may be given to the angles θ1 and θ2.

  The angle θ3 formed by the sipe 15 formed in the land portion 22 and the main groove 11 at the opening end to the main groove 11 on the shoulder side is set in a range of 30 ° to 90 °, and the sipe 17 formed in the land portion 23. Is the opening end to the main groove 11 on the shoulder side, and the angle θ4 formed with the main groove 11 is set in the range of 50 ° to 90 °. Thus, the angles θ3 and θ4 formed by the sipes 15 and 17 with respect to the main groove 11 are set in the same direction as the angles θ1 and θ2 of the lug grooves 14 and 16, and the lug grooves 14 and 16 and the sipes 15 and 17 do not intersect each other. By doing so, the cornering force resulting from the tread pattern can be generated in a direction that cancels the vehicle flow caused by the canting of the road surface, and the steering stability can be further improved.

  The tire size is 195 / 65R15, three main grooves extending linearly in the tire circumferential direction are provided on the tread surface, and linearly extending in the tire circumferential direction on both sides of the main groove located at the center of the tread surface. Two sub-grooves that are narrower and narrower than the entire main groove are provided, and a first land portion sandwiched between the sub-groove and the central main groove is defined in a central region defined inside the sub-grooves. A second land portion sandwiched between the auxiliary groove and the main groove on the shoulder side and a third land portion located outside the main groove on the shoulder side are defined in an outer region defined on the outer side of the first land, A plurality of shallow grooves are provided in the part, a plurality of lug grooves are provided in the second land part, the third land part is divided into a plurality of blocks, and a plurality of lug grooves are provided in the third land part. The third land portion is provided and divided into a plurality of blocks, and both side wall surfaces of each main groove are chamfered, and a cross section of the chamfer portion The outer shape is an arc in contact with the tread surface, the groove width GW1 at the tread surface of the main groove, the groove width GW2 at the central position in the depth direction of the main groove, the curvature radius R of the chamfered portion of the main groove, the maximum groove of the main groove Tires of Examples 1 and 2 having different depths GD1 and sub-groove depths GD2 as shown in Table 1 were produced. In addition, tires of Comparative Examples 1 and 2 in which a part of the above configuration was changed were prepared. Of the three main grooves, the two main grooves on the shoulder side have the same dimensions, and the main groove on the center side is narrower than the main groove on the shoulder side.

  These test tires were evaluated for noise reduction effect, wandering phenomenon suppression effect, straight running hydroplaning prevention performance, and steering stability by the following test methods, and the results are also shown in Table 1.

Noise reduction effect:
A test tire is mounted on a wheel with a rim size of 15 × 6J, mounted on a test vehicle with an air pressure of 200 kPa, traveled at 100 km / h on a road surface where noise in the high frequency region is likely to occur, and a microphone installed on the driver's seat window side is used. Thus, the sound pressure level at a frequency of 1 kHz where the influence of air column resonance in the main groove is large was measured. The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. A larger index value means less noise.

Wandering phenomenon suppression effect:
The test tire was assembled on a wheel with a rim size of 15 × 6 J and mounted on a test vehicle with an air pressure of 200 kPa, and the feeling of the handle being taken off and the vehicle's wobbling on the rain groove road surface was evaluated. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the greater the wandering phenomenon suppression effect.

Hydroplaning prevention performance when going straight:
The test tire is mounted on a wheel with a rim size of 15 x 6 J, the air pressure is set to 200 kPa, this is mounted on the fifth test wheel installed in the test vehicle, and the running speed is gradually increased on a straight path with a water depth of 10 mm. The minimum speed at which the slip rate of the test tire obtained from the vehicle speed and the rotational speed of the test tire reached 10% was measured. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the anti-hydroplaning performance when going straight.

Steering stability:
The test tire was mounted on a wheel with a rim size of 15 × 6 J and mounted on a test vehicle with an air pressure of 200 kPa, and the steering stability when going straight and when changing the lane was evaluated. The evaluation results are shown as an index with Comparative Example 1 as 100. The larger the index value, the better the steering stability.

  As can be seen from Table 1, the tires of Examples 1 and 2 have a noise reduction effect and wandering while maintaining good hydroplaning prevention performance during straight running and steering stability in comparison with Comparative Examples 1 and 2. The effect of suppressing the phenomenon was sufficiently obtained.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which shows the outline in the meridian section of the pneumatic tire of FIG. It is sectional drawing which shows the outline in the meridian section of the main groove and subgroove in the pneumatic tire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 11 Main groove 11a Chamfering part 12 Sub groove 13 Shallow groove 14,16 Lag groove 15,17 Sipe 21 Land part (1st land part)
22 Land (second land)
23 Land (third land)
A1 Central area A2 Outer area

Claims (13)

  The tread surface is provided with at least three main grooves extending linearly in the tire circumferential direction, and extends linearly in the tire circumferential direction on both sides of the main groove located at the center of the tread surface, and is narrower and narrower than all the main grooves. The secondary grooves are provided, a first land portion sandwiched between the secondary groove and the central main groove is defined in a central region defined inside the secondary grooves, and is defined outside the secondary grooves. A plurality of lug grooves that divide a second land portion sandwiched between the sub-groove and the shoulder-side main groove in an outer region and open to the sub-groove and the shoulder-side main groove in the second land portion. The second land portion is divided into a plurality of blocks, and at least one side wall surface of each main groove is chamfered, and the cross-sectional contour shape of the chamfered portion is an arc in contact with the tread surface. Ratio of groove width GW2 at the center position in the depth direction to groove width GW1 on the tread surface of the groove A pneumatic tire which was 30% to 55% a.   The pneumatic tire according to claim 1, wherein a total sum of the groove widths GW1 on the tread surfaces of all the main grooves is 20% to 35% of the contact width TW of the tread surface.   The pneumatic tire according to claim 1 or 2, wherein the radius of curvature R of the chamfered portion of each main groove is 10% to 35% of the groove width GW1 at the tread surface of each main groove.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove depth GD2 of the sub groove is set to 30% to 60% of a maximum groove depth GD1 of all main grooves.   The first land portion is provided with a plurality of shallow grooves that open to the sub-groove and the central main groove, and the depth of these shallow grooves is equal to or less than the groove depth of the sub-groove. The pneumatic tire according to any one of claims 1 to 4.   The groove depth of the lug groove formed in the second land portion is made larger on the shoulder side than the center side of the tread surface, and the largest groove depth GD1 of all the main grooves and the groove depth of the sub-grooves The pneumatic tire according to claim 5, wherein the pneumatic tire is set in a range between GD2.   The second land block is provided with a sipe that opens at least in the main groove on the shoulder side, the depth of the sipe is constant or larger on the shoulder side than the center side of the tread surface, and the second The pneumatic tire according to claim 6, wherein the pneumatic tire is smaller than the depth of the deepest portion of the lug groove formed in the land portion.   A third land portion located outside the main groove on the shoulder side is defined in the outer region, and the pattern region end of the tread surface is grounded while opening in the main groove on the shoulder side in the third land portion. The pneumatic tire according to any one of claims 1 to 7, wherein a plurality of lug grooves extending to a section between the region ends are provided.   The third land portion is provided with a plurality of sipes extending to a section between the pattern region end and the grounding region end of the tread surface while opening the main groove on the shoulder side, and the groove at the deepest portion of the sipes The pneumatic tire according to claim 8, wherein the depth is made smaller than the depth of the deepest portion of the lug groove formed in the third land portion.   The angle θ1 that the lug groove formed in the second land portion forms with the main groove at the opening end to the main groove on the shoulder side is set in a range of 30 ° to 70 °. Pneumatic tire described in 2.   The angle θ2 formed by the lug groove formed in the third land portion with the main groove at the opening end to the main groove on the shoulder side is set in a range of 50 ° to 85 °. Pneumatic tire described in 2. The angles θ1 and θ2 are each changed to the two or more values and changed in the tire circumferential direction, and the relationship θ1 _max <θ2 _min is established between the maximum value θ1 _max of the angle θ1 and the minimum value θ2 _min of the angle θ2. The pneumatic tire according to claim 11.   An angle θ3 formed by the sipe formed on the second land portion with the main groove at the opening end to the main groove on the shoulder side is set in a range of 30 ° to 90 °, and formed on the third land portion. The pneumatic tire according to any one of claims 7 to 12, wherein an angle θ4 that the formed sipe forms with the main groove at an opening end to the main groove on the shoulder side is set in a range of 50 ° to 90 °.

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